I. Field of the Invention
This invention relates to a tire endurance testing machine for testing various characteristics and endurance of tires by loading a tire with a slip angle and a camber angle to a rotating drum.
II. Description of the Related Art
As shown in FIGS. 1 to 3, a conventional tire endurance testing machine 50 has a rotatable drum on one side of the main frame 52, to which drum a tire 54 is loaded. The drum 56 is rotated by an electromotor through a timing belt or the like, which are not shown. Two load carriage guides 58a and 58b are suspended in parallel in the up-and-down direction between the vertical frames 52a and 52b. A tire loading carriage 60 is movably provided on the load carriage guides 58a and 58b. A carriage arm 62 is rotatably mounted on the tire loading carriage 60 by means of a carriage arm-supporting axle 64. An assembled tire spindle 66 is rotatably provided on the tip of the carriage arm 62 by means of an assembled tire spindle-supporting axles 68a and 68b. A tire 54 is mounted on a tire spindle 70 of the assembled tire spindle 66.
A loading hydraulic cylinder 72 which pushes the tire loading carriage 60 to the direction of the outer surface of the drum is provided on the vertical frame 52a of the main frame 52. An actuating cylinder for slip angle 74 which gives a slip angle to the carriage arm 62 is provided on the tire loading carriage 60. An actuating cylinder for camber angle 76 which gives a camber angle to the assembled tire spindle 66 is provided on the carriage arm 62.
In operation for determining various characteristics and endurance of the tire 54, the tire 54 is mounted on the tire spindle 70 of the assembled tire spindle 66 and the carriage arm 62 is rotated by the actuating cylinder for slip angle 74 to provide a prescribed slip angle to the tire 54. At the same time, the assembled tire spindle 66 is rotated by the actuating cylinder for camber angle 76 to provide a prescribed camber angle to the tire 54 and the tire loading carriage 60 is pushed with a prescribed load by the loading hydraulic cylinder 72 so as to load the tire 54 to the outer surface of the drum 56. In these conditions, the drum 56 is rotated and the various characteristics and endurance of the tire 54 are determined.
In the above-described conventional tire endurance testing machine 50, the assembled tire spindle-supporting axles (hereinafter referred to as "camber axles" for short) 68a and 68b for giving the camber angle to the tire 54 is located at the tip portion of the carriage arm 62, so that it is located away from the carriage arm-supporting axle 64 which gives the slip angle to the carriage arm 62. As a result, when the assembled tire spindle 66 is rotated by the actuating cylinder for camber angle 76, the center of the contact portions 54a and 56a of the outer surface of the drum 56 with the tire 54 is shifted from the center line CL to the position designated by the reference numerals 54b and 56a, which center line CL is coincidence with the axis of the carriage arm-supporting axle 64 and which penetrates the center of the outer surface of the drum 56. Thus, when the camber angle and the slip angle are simultaneously given to the tire 54, the tire 54 contacts the drum 56 at a portion shifted from the center line CL. If the camber angle and/or the slip angle is large, by the influence of the curvature of the drum 56, the direction in which the tire 54 is loaded to the drum 56 and the direction in which the reaction by the drum 56 is exerted are changed, so that the strength of the force exerted to the tire 54 by the operation of the cylinders 72, 74 and 76 becomes different from the strength of the reaction by the drum 56, which is received by the tire 54. Thus, the camber angle and the slip angle, as well as the load cannot be given to the tire 54 under precise control.